The Subfamily Lampyrinae fireflies are distributed over the Oriental realm. Lamprigera tenebrosa (Walker, 1858) is one of the Lampyrinae which were originally described from Sri Lanka (as Ceylon). However, their systematics and biology have not been explored to any extent after they were first described in early eighteenth.  Lamprigera tenebrosa was collected from grasslands, paddy fields, and freshwater associated lands from all nine Provinces of Sri Lanka in the study. The present paper describes the systematics and biology of the found male, female, larvae, and eggs of L. tenebrosa in Sri Lanka. The apterous female and larvae were identified when they were associating with males in the same habitats. Descriptions of their areas of incidence in Sri Lanka with indications of habitat types are included. The flashing differences and other behavioral aspects observed during the study are addressed here. The information of the study will be helpful for taxonomists, researchers who are interested in further studies on this group.